Investigation of the Mechanical, Electronic and Phonon Properties of X2ScAl (X = Ir, Os, and Pt) Heusler Compounds

In the present study, the second-order elastic constants and the electronic band structures of the X 2 ScAl ( x = Ir, Os, and Pt) compounds crystallized in the L2 1 phase were calculated separately by using the ab-initio density functional theory. According to the results for the second-order elastic constants, these compounds met the Born mechanical stability criteria. Also, according to the Pugh criteria, they were found to have a ductile structure and to show anisotropic behavior. The microhardneses of the compounds were between 2 and 14 GPa, and the highest hardness was found in the Ir 2 ScAl (14.290 GPa) compound. In addition, the energy band structures of these compounds were calculated, and the crystals were found to have a metallic bond structure. All the computed data were compared with previously calculated results obtained with different methods. According to the findings obtained in the present study, in terms of its mechanical and electronic behaviors, Ir 2 ScAl was found to have better physical properties than Os 2 ScAl and Pt 2 ScAl. The phonon dispersion curves and their corresponding total and projected densities of states were investigated for the first time by using a linear-response approach in the context of density functional perturbation theory. The frequencies of the optical phonon modes of all compounds at the Γ point were 4.767, 7.504 and 9.271 THz for Ir 2 ScAl, 2.761, 7.985 and 9.184 THz for Os 2 ScAl and 2.012, 5.6952 and 8.118 THz for Pt 2 ScAl. The heat capacity C v at constant volume versus temperature was calculated using a quasi-harmonic approach and the results are discussed.